Catheters have found widespread use in medical procedures, such as percutaneous transluminal coronary angioplasty (PTCA) or for delivery of stents. Most catheters are guided to the application site by sliding the catheter along a guide wire, which has been carefully advanced and arranged within the patient. During advancement of the catheter along the guide wire, it is important to keep the guide wire steady. Ordinary catheters are guided to the application site in a patient by sliding the catheter along a guide wire extending all the way through a lumen of the catheter from the proximal end to the distal end thereof. To enable the physician to hold or manipulate the guide wire during advancement of the catheter along the guide wire, it is necessary to have an excess length of guide wire. The guide wire must hence have a length of about twice the length of the catheter, e.g. 3 m in total, which greatly impedes the procedure. An important sub-category of catheters are catheters of the well-known so-called rapid exchange type, which greatly facilitate operation, especially exchange of catheters if it is found during a procedure that a different kind or size of catheter is needed for the specific purpose. In the rapid exchange catheter, the guide wire only passes through a minor part of the catheter at the distal end thereof, whereas along a majority of the catheter, the guide wire runs in parallel with the catheter. Hence it is not necessary to have an excess length of guide wire. However the rapid exchange catheter provides some challenges, especially with regard to resistance to kinking of the catheter.
An important feature of catheters is the transmission of force, the so-called push force, from the proximal end to the distal end of the catheter. This transmission significantly affects the physician's ability to direct the distal end of the catheter into a body lumen of a patient by manipulating the proximal end thereof. Another important feature of catheters is the flexibility of the distal end to bend and conform to the body lumen wall without causing any injury to the lumen wall. Hence catheters, especially of the rapid exchange type, are commonly manufactured of a metal proximal shaft portion of relatively stiffness, and a relatively flexible plastics distal portion bonded to the metal shaft portion. An abrupt change of properties between the shaft portion and the distal portion however increases the risk of twist and kinking. Hence there is a need to provide a good transition between the relatively stiff proximal section to the relatively more flexible distal section to provide a sufficient resistance to twist and kinking while maintaining flexibility and ability to bend.
U.S. Pat. No. 6,746,423 discloses a catheter with a reinforcing member at a rapid exchange junction. Although this construction has some effect on the kink resistance, it is somewhat difficult to manufacture and hence expensive. This is due to the fact that the construction introduces a separate element, namely a reinforcing member, which must be securely bonded to the catheter. The reinforcing member must be stocked and handled inevitably raising the cost, and further there is an increased risk of leakage from the catheter due to the extra joints, thereby raising the costs to skilled personnel and quality check.
It is hence an object of the invention to provide an alternative catheter with reduced risk of kinking.